Add 6 new tools: Hasher, Base64, JWT Decoder, Password Gen, Timestamp, Text Diff

- backend/tools/hasher.py: POST /api/hash/sha256 and /api/hash/bcrypt (bcrypt added to requirements)
- backend/tools/base64tool.py: POST /api/base64/encode and /api/base64/decode
- backend/tools/jwtdecoder.py: POST /api/jwt/decode (signature verification disabled)
- backend/tools/passwordgen.py: POST /api/password/generate with charset and length options
- backend/tools/timestamp.py: POST /api/timestamp/convert (unix<->date, ISO 8601 + German format)
- backend/tools/textdiff.py: POST /api/text/diff returning structured added/removed/unchanged lines
- All blueprints registered in app.py and tools/__init__.py
- React components with copy button, dark/light mode support via CSS variables
- ToolOverview rebuilt as card grid; App.jsx routes added for all tools

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/tools/passwordgen.py

@@ -0,0 +1,41 @@
+from flask import Blueprint, request, jsonify
+import secrets
+import string
+from util.logger import logger
+from auth.token import verify_token
+
+passwordgen_blueprint = Blueprint('passwordgen_tool', __name__)
+
+
+@passwordgen_blueprint.route('/api/password/generate', methods=['POST'])
+def generate_password():
+    user = verify_token()
+    if not user:
+        return jsonify({"message": "Nicht autorisiert"}), 401
+    try:
+        data = request.get_json()
+        length = min(max(int(data.get("length", 16)), 8), 64)
+        use_uppercase = data.get("uppercase", True)
+        use_lowercase = data.get("lowercase", True)
+        use_numbers = data.get("numbers", True)
+        use_symbols = data.get("symbols", False)
+
+        charset = ""
+        if use_uppercase:
+            charset += string.ascii_uppercase
+        if use_lowercase:
+            charset += string.ascii_lowercase
+        if use_numbers:
+            charset += string.digits
+        if use_symbols:
+            charset += string.punctuation
+
+        if not charset:
+            return jsonify({"message": "Mindestens ein Zeichensatz muss ausgewählt sein"}), 400
+
+        password = ''.join(secrets.choice(charset) for _ in range(length))
+        logger.info(f"Passwort generiert von {user['username']}")
+        return jsonify({"password": password})
+    except Exception as e:
+        logger.error(f"Fehler Passwortgenerator: {e}")
+        return jsonify({"message": "Fehler beim Generieren"}), 500